Non-lithotripsic kidney-stone therapy

ABSTRACT

One aspect of the present invention relates to a method of using peristalsis to force a polymer plug through a mammalian lumen, thereby removing any calculi and/or calculi fragments present in the lumen. In one embodiment, the method is used as an alternative to conventional lithotripsy. In another embodiment, the method is used in conjunction with lithotripsy, thereby removing the small calculi fragments that result from such procedures.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/259,103, filed Apr. 22, 2014, which is a continuation of U.S.application Ser. No. 13/714,933, filed Dec. 14, 2012, now abandoned,which is a continuation of U.S. application Ser. No. 11/412,407, filedApr. 27, 2006, now U.S. Pat. No. 8,361,455, issued Jan. 29, 2013, whichclaims the benefit of U.S. Provisional Application No. 60/676,757, filedon May 2, 2005. The entire teachings of the above applications areincorporated herein by reference.

BACKGROUND OF THE INVENTION

Lithiasis is a common human ailment characterized by calculi or “stones”formed within a passage of the human body. While stones have beendocumented in just about every passage within the body, kidney stones(nephrolithiasis) and gallstones (cholelithiasis) remain the mostcommon. Regardless of its location, however, a stone is typically anextremely hard and unyielding mass which blocks the passage (e.g.,lumen) in which it presents.

Calculi or stones in the urinary tract or kidneys usually arise becauseof the breakdown of a delicate balance in the body. Specifically, thekidneys must conserve water to function, but they must excrete materialsthat have a low solubility. These opposing requirements must be balancedduring adaptation to diet, climate and activity. The problem ismitigated to some degree because urine contains substances that inhibitcrystallization of stone-forming minerals. However, when urine becomessupersaturated with insoluble materials, because excretion rates areexcessive and/or because water conservation is extreme, crystals formand may grow and aggregate to form a stone.

Although small crystals are readily voided from the kidney with urine,the larger stones frequently become dislodged from the kidney and enterthe ureter or occlude the uretero-pelvic junction, causing obstructionand pain. Although some stones can ultimately traverse the ureter, theirpassage typically produces pain and bleeding. Usually, the pain is sosevere that narcotic drugs are needed for its control.

Removal of stones from the kidneys or urinary tract can be effectedmedically, mechanically or surgically. A well-known surgical approachinvolves passing a flexible basket in a retrograde manner up the ureterfrom the bladder, and using the basket to capture the stones. However,the baskets require post-capture removal and only work well formedium-sized stones. Surgery has also been used to remove kidney stones,especially so-called staghorn stones which get lodged in the ureter.

Another surgical technique, percutaneous ultrasonic lithotripsy,requires the passage of a rigid cystoscopy-like instrument in the renalpelvis through a small incision in the flank whereupon stones are brokenup by a small ultrasound transducer and then removed directly. Anothersurgical technique is laser lithotripsy via a ureteroscope. All of theseprocedures, which can be quite painful, are elaborate and expensive, andthey do not always result in complete removal of the stones andfragments. One non-invasive technique, known as extracorporeallithotripsy, entails transmission of high-intensity shock waves fromoutside the body to fragment the stones within the body. The resultingstone fragments are then voided with urine.

Stents have also been used to decompress ureteral obstructions, ensuringthat urine drains from the kidney to the bladder. It was recognized thatplacement of a stent within the ureter could help small stones and stonefragments to transit the ureter. In a typical procedure involving astent, a guide wire is passed through the ureter to the renal pelvis. Ahollow, flexible, cylindrical stent is then advanced with a pusher overthe guide wire. The guide wire and pusher are then extracted from thestent and the body, leaving an open lumen for urine to pass through.However, because the lumen defined by the cylindrical stent is evensmaller than the ureter itself, all but the smallest stones and sludgeare precluded from passing through. In many cases, stone fragments oftenblock the open stent passageway.

SUMMARY OF THE INVENTION

One aspect of the present invention provides an approach to thetreatment of lithiasis. In one embodiment, the instant inventionprovides a method of using peristalsis to force a polymer plug through amammalian lumen, thereby removing any calculi and/or calculi fragmentspresent in the lumen. In one embodiment this method is used as analternative to conventional lithotripsy. In another embodiment thismethod is used subsequent to lithotripsy, removing the small fragmentsthat result from such procedures. In certain embodiments, the polymerplug is generated in situ by one or more physical phenomena, such astemperature, pH change and/or ionic interactions. In certain embodimentsthe polymer plug rapidly dissolves after passing through the lumen.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 depicts the deployment of a catheter into a lumen containing acalculi.

FIG. 2 depicts one embodiment of the deployment of a polymer in a lumenat a position upstream from a calculi.

FIG. 3 depicts the position of the polymer plug and calculi beforeperistaltic motion.

FIG. 4 depicts the effect of peristalsis (i.e. the movement of thepolymer plug towards the outlet of the lumen and the resulting expulsionof the calculi).

FIG. 5 depicts dissolution times under static conditions for purifiedpoloxamer 407 as function of concentration (see Example 3).

DETAILED DESCRIPTION OF THE INVENTION

One aspect of the present invention provides an approach to thetreatment of lithiasis. Importantly, the present invention mitigates therisk of damage to surrounding body tissue when removing a calculi (e.g.,biological concretions such as urinary, biliary, and pancreatic stones)which obstructs or may otherwise be present within a body's anatomicallumen. Remarkably, the present invention improves significantly thetreatment of lithiasis, while simultaneously reducing the risk of tissuedamage and decreasing the procedure time.

In one embodiment, the instant invention provides a method of using anon-tissue adhesive polymer plug to partially or completely occlude alumen and using the plug to remove calculi and/or calculi fragments fromthe lumen through the passage of the polymer plug through the lumen dueto the natural action of peristalsis on the polymer plug. In oneembodiment the method is used as an alternative to conventionallithotripsy. In another embodiment the method is used subsequent tolithotripsy, to remove the small fragments that result from suchprocedures. In certain embodiments the polymer plug is generated in situby one or more physical phenomena, such as temperature, pH changesand/or ionic interactions. In some of these embodiments a dual lumencatheter is utilized to inject two solutions proximal to the stone, themixing of said solutions causing a polymer plug to form. In certainembodiments the polymers used in the methods of the invention areinverse thermosensitive polymers. In other embodiment, gel formation dueto ionic charges may be used to form a polymer plug. In certainembodiments the polymer plug rapidly dissolves, e.g., in the bladder,after being passed through the lumen.

Definitions

For convenience, certain terms employed in the specification,exemplification, and appended claims are collected here.

The articles “a” and “an” are used herein to refer to one or to morethan one (i.e., to at least one) of the grammatical object of thearticle. By way of example, “an element” means one element or more thanone element.

The terms “reversibly gelling” and “inverse thermosensitive” refer tothe property of a polymer wherein gelation takes place upon an increasein temperature, rather than a decrease in temperature.

The term “transition temperature” refers to the temperature ortemperature range at which gelation of an inverse thermosensitivepolymer occurs.

The term “contrast-enhancing” refers to materials capable of beingmonitored during injection into a mammalian subject by methods formonitoring and detecting such materials, for example by radiography orfluoroscopy. An example of a contrast-enhancing agent is a radiopaquematerial. Contrast-enhancing agents including radiopaque materials maybe either water soluble or water insoluble. Examples of water solubleradiopaque materials include metrizamide, iopamidol, iothalamate sodium,iodomide sodium, and meglumine. Examples of water insoluble radiopaquematerials include metals and metal oxides such as gold, titanium,silver, stainless steel, oxides thereof, aluminum oxide, zirconiumoxide, etc.

As used herein, the term “polymer” means a molecule, formed by thechemical union of two or more oligomer units. The chemical units arenormally linked together by covalent linkages. The two or more combiningunits in a polymer can be the same, in which case the polymer isreferred to as a homopolymer. They can be also be different and, thus,the polymer will be a combination of the different units; these polymersare referred to as copolymers.

As used herein, “crosslinking” is when individual polymer chains arelinked together by covalent bonds (“chemical crosslinking”) or ionicbonds (“ionic crosslinking”) to form a three dimensional network. Incertain polymers this kind of process has the effect of producing a gel.

The term “biocompatible”, as used herein, refers to having the propertyof being biologically compatible by not producing a toxic, injurious, orimmunological response in living tissue. The term “non-tissue adhesive”,as used herein denotes a substance (e.g. a polymer plug) does not adhereto biological tissue.

The term “poloxamer” denotes a symmetrical block copolymer, consistingof a core of PPG polyoxyethylated at both of its terminal hydroxylgroups, i.e., conforming to the interchangeable generic formula(PEG)_(X)-(PPG)_(Y)-(PEG)_(X) and (PEO)_(X)-(PPO)_(Y)-(PEO)_(X). Eachpoloxamer name ends with an arbitrary code number, which is related tothe average numerical values of the respective monomer units denoted byX and Y.

The term “poloxamine” denotes a polyalkoxylated symmetrical blockcopolymer of ethylene diamine conforming to the general type[(PEG)_(X)-(PPG)_(Y)]₂-NCH₂CH₂N—[(PPG)_(Y)-(PEG)_(X)]₂. Each Poloxaminename is followed by an arbitrary code number, which is related to theaverage numerical values of the respective monomer units denoted by Xand Y.

The term “inverse thermosensitive polymer” as used herein refers to apolymer that is soluble in water at ambient temperature, but at leastpartially phase-separates out of water at physiological temperature.Inverse thermosensitive polymers include poloxamer 407, poloxamer 188,Pluronic® F127, Pluronic® F68, poly(N-isopropylacrylamide), poly(methylvinyl ether), poly(N-vinylcaprolactam); and certainpoly(organophosphazenes). See Bull. Korean Chem. Soc. 2002, 23, 549-554.

“Alginic acid” as used here in is a naturally occurring hydrophiliccolloidal polysaccharide obtained from the various species of brownseaweed (Phaeophyceae). It occurs in white to yellowish brownfilamentous, grainy, granular or powdered forms. It is a linearcopolymer consisting mainly of residues of β-1,4-linked D-mannuronicacid and α-1,4-linked L-glucuronic acid. These monomers are oftenarranged in homopolymeric blocks separated by regions approximating analternating sequence of the two acid monomers, as shown below:

The formula weight of the structural unit is 176.13 (theoretical; 200 isthe actual average). The formula weight of the macromolecule ranges fromabout 10,000 to about 600,000 (typical average).

“Sodium alginate” and “potassium alginate” are salts of alginic acid.For example, “potassium alginate” is shown below:

“Gellan gum” is a high molecular weight polysaccharide gum produced by apure culture fermentation of a carbohydrate by Pseudomonas elodea,purified by recovery with isopropyl alcohol, dried, and milled. The highmolecular weight polysaccharide is principally composed of atetrasaccharide repeating unit of one rhamnose, one glucuronic acid, andtwo glucose units, and is substituted with acyl (glyceryl and acetyl)groups as the O-glycosidically-linked esters. The glucuronic acid isneutralized to a mixed potassium, sodium, calcium, and magnesium salt.It usually contains a small amount of nitrogen containing compoundsresulting from the fermentation procedures. It has a formula weight ofabout 500,000. “Sodium gellan” and “potassium gellan” are salts ofgellan gum.

Carboxymethylcellulose (CMC) is a polymer derived from naturalcellulose. Unlike cellulose, CMC is highly water-soluble. The CMCstructure is based on the b-(1®4)-D-glucopyranose polymer of cellulose.Different preparations may have different degrees of substitution, butit is generally in the range 0.6-0.95 derivatives per monomer unit, asshown below: acc

CMC molecules are somewhat shorter, on average, than native cellulosewith uneven derivatization giving areas of high and low substitution.This substitution is mostly 2-O- and 6-O-linked, followed in order ofimportance by 2,6-di-O- then 3-O-, 3,6-di-O-, 2,3-di-O- lastly2,3,6-tri-O-linked. It appears that the substitution process is aslightly cooperative (within residues) rather than random process givingslightly higher than expected unsubstituted and trisubstituted areas.CMC molecules are most extended (rod-like) at low concentrations but athigher concentrations the molecules overlap and coil up and then, athigh concentrations, entangle to become a thermoreversible gel.Increasing ionic strength and reducing pH both decrease the viscosity asthey cause the polymer to become more coiled. The average chain lengthand degree of substitution are of great importance; the more-hydrophobiclower substituted CMCs are thixotropic but more-extended highersubstituted CMCs are pseudoplastic. At low pH, CMC may form cross-linksthrough lactonization between carboxylic acid and free hydroxyl groups.

“Poly vinyl alcohol” (PVA) is a water soluble polymer synthesized byhydrolysis of a poly vinyl ester such as the acetate and used forpreparation of fibers. PVA a thermoplastic that is produced from full orpartial hydrolysis of vinyl ester such as vinyl acetate resulting in thereplacement of some or all of the acetyl groups with hydroxyl groups.For example:

In certain embodiments polyvinyl alcohol (PVA) is a synthetic resinproduced by polymerisation of vinyl acetate (VAM) followed by hydrolysisof the polyvinyl acetate (PVAc) polymer. The degree of polymerisationdetermines the molecular weight and viscosity in solution. The degree ofhydrolysis (saponification) signifies the extent of conversion of thePolyvinyl Acetate to the Polyvinyl Alcohol For example n (Degree ofHydrolysis) may be in the range of about 68.2 to about 99.8 mol. % andthe MW (Weight Average Molecular Weight) may range from about 10.000 toabout 190,000.

Hyaluronic acid (HA) is a polymer composed of repeating dimeric units ofglucuronic acid and N-acetyl glucosamine. It may be of extremely highmolecular weight (up to several million daltons) and forms the core ofcomplex proteoglycan aggregates found in extracellular matrix. HA iscomprised of linear, unbranching, polyanionic disaccharide unitsconsisting of glucuronic acid (GlcUA) an N-acetyl glucosamine (GlcNAc)joined alternately by β-1-3 and β-1-4 glycosidic bonds (see below). Itis a member of the glycosaminoglycan family which includes chondroitinsulphate, dermatin sulphate and heparan sulphate. Unlike other membersof this family, it is not found covalently bound to proteins.

When incorporated into a neutral aqueous solution hydrogen bondformation occurs between water molecules and adjacent carboxyl andN-acetyl groups. This imparts a conformational stiffness to the polymer,which limits its flexibility. The hydrogen bond formation results in theunique water-binding and retention capacity of the polymer. It alsofollows that the water-binding capacity is directly related to themolecular weight of the molecule. Up to six liters of water may be boundper gram of HA.

HA solutions are characteristically viscoelastic and pseudoplastic. Thisrheology is found even in very dilute solutions of the polymer wherevery viscous gels are formed. The viscoelastic property of HA solutionswhich is important in its use as a biomaterial is controlled by theconcentration and molecular weight of the HA chains. The molecularweight of HA from different sources is polydisperse and highly variableranging from 10⁴ to 10⁷ Da. The extrusion of HA through the cellmembrane as it is produced permits unconstrained polymer elongation andhence a very high molecular weight molecule.

The phrase “polydispersity index” refers to the ratio of the “weightaverage molecular weight” to the “number average molecular weight” for aparticular polymer; it reflects the distribution of individual molecularweights in a polymer sample.

The phrase “weight average molecular weight” refers to a particularmeasure of the molecular weight of a polymer. The weight averagemolecular weight is calculated as follows: determine the molecularweight of a number of polymer molecules; add the squares of theseweights; and then divide by the total weight of the molecules.

The phrase “number average molecular weight” refers to a particularmeasure of the molecular weight of a polymer. The number averagemolecular weight is the common average of the molecular weights of theindividual polymer molecules. It is determined by measuring themolecular weight of n polymer molecules, summing the weights, anddividing by n.

The terms “calculi” and “calculus” denote one or more masses or nodulesof solid matter formed by growing together, by congelation,condensation, coagulation, induration, etc. Common synonyms, forexample, are concretions, stones, clots, tones or lumps. Often, in anorganism a concretion is a hard lump of mineral salts found in a holloworgan or duct. In one embodiment, concretion refers to stone-likeobjects found within an organ (e.g., the kidneys) of an organism.

The term “lumen” denotes the space enclosed by a tube-like structure orhollow organ, such as inside an artery, a vein, a kidney, a gallbladder, a ureter, a urinary bladder, a pancreas, a salivary gland, asmall intestine or a large intestine (i.e., an opening, space, or cavityin a biological system). A lumen has an “inlet” and an “outlet” based onthe direction of the flow of materials through the lumen. As used here“upstream” from a given object in a lumen means between said object andthe inlet of the lumen; “downstream” from a given object in a lumenmeans between said object and the outlet of the lumen.

“Peristalsis” as used herein refers to a series of coordinated, rhythmicmuscle contractions. For example, it is an automatic and vital processthat moves food through the digestive tract, urine from the kidneysthrough the ureters into the bladder, and bile from the gallbladder intothe duodenum. Peristalsis moves material in a lumen towards the outletof the lumen.

“Lithotripsy” as used herein refers to any procedure, surgery ortechnique that fragments or breaks up a stone.

“Lithiasis” as used herein refers to a common human ailmentcharacterized by calculi or “stones” formed within a passage or lumen ofa human.

Calculi

Calculi can develop in parts of the body, such as in the kidneys,pancreas, ureter and gallbladder. It is not uncommon for biologicalcalculi to be referred to as stones, especially when they are composedof mineral salts. For example, calculi formed in the biliary system arecalled gallstones. Those that form in the bladder are often known asvesical calculi or bladder stones. Calculi occurring in the kidney areoften called kidney stones. Calculi can also occur in the ureter; therethey are usually the result of the incomplete passage of a calculioriginating in a kidney. It is also possible to observe a calculi in asalivary duct or gland.

There are four main types of calculi observed biologically. The majorityof calculi, about 75%, are calcium-containing, composed of calciumoxalate, sometimes mixed with calcium phosphate. Another 15% arecomposed of magnesium ammonium phosphate; these calculi are oftenreferred to as “triple stones” or struvite stones. The bulk of theremaining stones are made up of uric acid or cystine (Cys-Cys). Asmentioned above, when calculi are too large to pass spontaneously,medical intervention is often needed.

Polymers of the Invention

In certain embodiments a polymer plug is generated in situ by one ormore physical phenomena, such as temperature, pH changes and/or ionicinteractions. In other embodiment, the polymers used in a method of theinvention are crosslinkable polymers. In certain embodiments the polymerplug generate in situ is non-tissue adhesive.

In one embodiment two solutions, a polymer solution and a crosslinkersolution, are injected separately (e.g., through a dual lumen catheter)into a biological lumen wherein they gel, forming a polymer plug. Saidpolymer solution may comprise an anionic polymer, a cationic polymer ora non-ionically crosslinkable polymer. Such polymers may comprise one ormore of the following: alginic acid, sodium alginate, potassiumalginate, sodium gellan, potassium gellan, carboxy methyl cellulose,hyaluronic acid, and polyvinyl alcohol. The cross-linking of the polymerto form a polymer plug may be achieved with anionic crosslinking ions,cationic crosslinking ions, or non-ionic crosslinking agents.Crosslinking agents include, but are not limited to, one or more of thefollowing: phosphate, citrate, borate, succinate, maleate, adipate,oxalate, calcium, magnesium, barium and strontium. Exemplary pairings ofpolymers and crosslinkers include anionic polymer monomers with cations,such as, for example, alginates with calcium, barium or magnesium;gellans with calcium, magnesium or barium; or hyaluronic acid withcalcium. An example of an exemplary pairing of a non-ionic polymer witha chemical crosslinking agent is a polyvinyl alcohol with borate (at aslightly alkaline pH).

In addition, in certain embodiments, the polymer plugs of the inventionmay be formed from an aqueous solution of one or more inversethermosensitive polymers. These polymer solutions are liquids below bodytemperature and gel at about body temperature. The polymer solution isprepared external of the body, i.e., at a temperature below bodytemperature. The polymer solution may be further chilled to prolong thetime the gel stays in the liquid form upon introduction into the body. Apreferred temperature is about 10° C. below the gelation temperature ofthe polymer solution.

In general, the inverse thermosensitive polymers used in the methods ofthe invention, which become a gel at or about body temperature, can beinjected into a patient's body in a liquid form. The injected materialupon reaching body temperature undergoes a transition from a liquid to agel. The inverse thermosensitive polymers used in connection with themethods of the invention may comprise a block copolymer with inversethermal gelation properties. The block copolymer can further comprise apolyoxyethylene-polyoxypropylene block copolymer, such as abiodegradable, biocompatible copolymer of polyethylene oxide andpolypropylene oxide. Also, the inverse thermosensitive polymer caninclude a therapeutic agent.

The molecular weight of the inverse thermosensitive polymer ispreferably between 1,000 and 50,000, more preferably between 5,000 and35,000. Preferably the polymer is in an aqueous solution. For example,typical aqueous solutions contain about 5% to about 30% polymer,preferably about 10% to about 25%. The molecular weight of a suitableinverse thermosensitive polymer (such as a poloxamer or poloxamine) maybe, for example, between 5,000 and 25,000, and more particularly between7,000 and 20,000.

The pH of the inverse thermosensitive polymer formulation administeredto the mammal is, generally, about 6.0 to about 7.8, which are suitablepH levels for injection into the mammalian body. The pH level may beadjusted by any suitable acid or base, such as hydrochloric acid orsodium hydroxide.

Suitable inverse thermosensitive polymers includepolyoxyethylene-polyoxypropylene (PEO-PPO) block copolymers. Twoexamples are Pluronic® F127 and F108, which are PEO-PPO block copolymerswith molecular weights of 12,600 and 14,600, respectively. Each of thesecompounds is available from BASF of Mount Olive, N.J. Pluronic® F108 at12-25% concentration in phosphate buffered saline (PBS) is an example ofa suitable inverse thermosensitive polymeric material. Pluronic® acidF127 at 12-25% concentration in PBS is another example of a suitablematerial. Low concentrations of dye (such as crystal violet), hormones,therapeutic agents, fillers, and antibiotics can be added to the inversethermosensitive polymer. In general, other biocompatible, biodegradablePEO-PPO block copolymers that exist as a gel at body temperature and aliquid at below body temperature may also be used according to thepresent invention.

Notably, Pluronic® polymers have unique surfactant abilities andextremely low toxicity and immunogenic responses. These products havelow acute oral and dermal toxicity and low potential for causingirritation or sensitization, and their general chronic and sub-chronictoxicity is low. In fact, Pluronic® polymers are among a small number ofsurfactants that have been approved by the FDA for direct use in medicalapplications and as food additives (BASF (1990) Pluronic® & Tetronic®Surfactants, BASF Co., Mount Olive, N.J.). Recently, several Pluronic®polymers have been found to enhance the therapeutic effect of drugs, andthe gene transfer efficiency mediated by adenovirus (March K L, MadisonJ E, Trapnell B C. “Pharmacokinetics of adenoviral vector-mediated genedelivery to vascular smooth muscle cells: modulation by poloxamer 407and implication for cardiovascular gene therapy” Hum. Gene Therapy 1995,6, 41-53).

The average molecular weights of the poloxamers range from about 1,000to greater than 16,000 daltons. Because the poloxamers are products of asequential series of reactions, the molecular weights of the individualpoloxamer molecules form a statistical distribution about the averagemolecular weight. In addition, commercially available poloxamers containsubstantial amounts of poly(oxyethylene) homopolymer andpoly(oxyethylene)/poly(oxypropylene diblock polymers. The relativeamounts of these byproducts increase as the molecular weights of thecomponent blocks of the poloxamer increase. Depending upon themanufacturer, these byproducts may constitute from about 15 to about 50%of the total mass of the polymer.

The inverse thermosensitive polymers may be purified using a process forthe fractionation of water-soluble polymers, comprising the steps ofdissolving a known amount of the polymer in water, adding a solubleextraction salt to the polymer solution, maintaining the solution at aconstant optimal temperature for a period of time adequate for twodistinct phases to appear, and separating physically the phases.Additionally, the phase containing the polymer fraction of the preferredmolecular weight may be diluted to the original volume with water,extraction salt may be added to achieve the original concentration, andthe separation process repeated as needed until a polymer having anarrower molecular weight distribution than the starting material andoptimal physical characteristics can be recovered.

In certain embodiments, a purified poloxamer or poloxamine has apolydispersity index from about 1.5 to about 1.0. In certainembodiments, a purified poloxamer or poloxamine has a polydispersityindex from about 1.2 to about 1.0. In certain embodiments, a purifiedpoloxamer or poloxamine has a polydispersity index from about 1.1 toabout 1.0.

The aforementioned process consists of forming an aqueous two-phasesystem composed of the polymer and an appropriate salt in water. In sucha system, a soluble salt can be added to a single phase polymer-watersystem to induce phase separation to yield a high salt, low polymerbottom phase, and a low salt, high polymer upper phase. Lower molecularweight polymers partition preferentially into the high salt, low polymerphase. Polymers that can be fractionated using this process includepolyethers, glycols such as poly(ethylene glycol) and poly(ethyleneoxide)s, polyoxyalkylene block copolymers such as poloxamers,poloxamines, and polyoxypropylene/polyoxybutylene copolymers, and otherpolyols, such as polyvinyl alcohol. The average molecular weight ofthese polymers may range from about 800 to greater than 100,000 daltons.See U.S. Pat. No. 6,761,824 (hereby incorporated by reference). Theaforementioned purification process inherently exploits the differencesin size and polarity, and therefore solubility, among the poloxamermolecules, the poly(oxyethylene) homopolymer and thepoly(oxyethylene)/poly(oxypropylene) diblock byproducts. The polarfraction of the poloxamer, which generally includes the lower molecularweight fraction and the byproducts, is removed allowing the highermolecular weight fraction of poloxamer to be recovered. The largermolecular weight poloxamer recovered by this method has physicalcharacteristics substantially different from the starting material orcommercially available poloxamer including a higher average molecularweight, lower polydispersity and a higher viscosity in aqueous solution.

Other purification methods may be used to achieve the desired outcome.For example, WO 92/16484 discloses the use of gel permeationchromatography to isolate a fraction of poloxamer 188 that exhibitsbeneficial biological effects, without causing potentially deleteriousside effects. The copolymer thus obtained had a polydispersity index of1.07 or less, and was substantially saturated. The potentially harmfulside effects were shown to be associated with the low molecular weight,unsaturated portion of the polymer, while the medically beneficialeffects resided in the uniform higher molecular weight material. Othersimilarly improved copolymers were obtained by purifying either thepolyoxypropylene center block during synthesis of the copolymer, or thecopolymer product itself (e.g., U.S. Pat. No. 5,523,492 and U.S. Pat.No. 5,696,298; both hereby incorporated by reference).

Further, a supercritical fluid extraction technique has been used tofractionate a polyoxyalkylene block copolymer as disclosed in U.S. Pat.No. 5,567,859 (hereby incorporated by reference). A purified fractionwas obtained, which was composed of a fairly uniform polyoxyalkyleneblock copolymer having a polydispersity of less than 1.17. According tothis method, the lower molecular weight fraction was removed in a streamof carbon dioxide maintained at a pressure of 2200 pounds per squareinch (psi) and a temperature of 40° C.

Additionally, U.S. Pat. No. 5,800,711 (hereby incorporated by reference)discloses a process for the fractionation of polyoxyalkylene blockcopolymers by the batchwise removal of low molecular weight speciesusing a salt extraction and liquid phase separation technique. Poloxamer407 and poloxamer 188 were fractionated by this method. In each case, acopolymer fraction was obtained which had a higher average molecularweight and a lower polydispersity index as compared to the startingmaterial. However, the changes in polydispersity index were modest andanalysis by gel permeation chromatography indicated that somelow-molecular-weight material remained. The viscosity of aqueoussolutions of the fractionated polymers was significantly greater thanthe viscosity of the commercially available polymers at temperaturesbetween 10° C. and 37° C., an important property for some medical anddrug delivery applications. Nevertheless, some of the low molecularweight contaminants of these polymers are thought to cause deleteriousside effects when used inside the body, making it especially importantthat they be removed in the fractionation process. As a consequence,polyoxyalkylene block copolymers fractionated by this process are notappropriate for all medical uses.

In a preferred embodiment, the polymers used are block polymers such aspolyoxyethylene-polyoxypropylene (PEO-PPO) block polymers of the generalstructure A-B, (A-B)_(n), A-B-A (e.g., Pluronic®), or (A-B-A)_(n) with Abeing the PEO part and B being the PPO part and n being greater than 1.In another preferred embodiment, the polymers used are branched polymersof polyoxyethylene-polyoxypropylene (PEO-PPO) like tetra-functionalpoloxamines (e.g., Tetronic®).

Methods of the Invention

The present invention provides an approach to the treatment oflithiasis. In one embodiment a polymer is injected between the inlet ofa lumen and a calculi in said lumen to form a polymer plug whichoccludes the lumen; the subsequent action of peristalsis causes thepolymer plug to traverse the lumen, forcing the calculi out of thelumen.

One aspect of the present invention relates to a method of treatinglithiasis, comprising the steps of:

injecting into a lumen of a mammal at a first position upstream from acalculi a first composition, wherein said first composition does notcontact said calculi; optionally injecting into said lumen at a secondposition upstream from said calculi a second composition, wherein saidsecond composition does not contact said calculi; thereby forming apolymer plug; and

allowing peristalsis to cause said polymer plug to traverse said lumen,thereby forcing said calculi from said lumen.

In certain embodiments, the present invention relates to theaforementioned method, wherein said second composition is injected intosaid lumen.

In certain embodiments, the present invention relates to theaforementioned method, wherein said first position is between about 1 cmand about 5 cm upstream of said calculi.

In certain embodiments, the present invention relates to theaforementioned method, wherein said first position is between about 2 cmand about 4 cm upstream of said calculi.

In certain embodiments, the present invention relates to theaforementioned method, wherein said first position is about 3 cmupstream of said calculi.

In certain embodiments, the present invention relates to theaforementioned method, wherein the distance between said first positionand said second position is less than about 3 mm.

In certain embodiments, the present invention relates to theaforementioned method, wherein the distance between said first positionand said second position is less than about 1 mm.

In certain embodiments, the present invention relates to theaforementioned method, wherein the distance between said first positionand said second position is less than about 0.5 mm.

In certain embodiments, the present invention relates to theaforementioned method, wherein the distance between said first positionand said second position is less than about 0.1 mm.

In certain embodiments, the present invention relates to theaforementioned method, wherein said first composition is injected intosaid lumen through a percutaneous access device.

In certain embodiments, the present invention relates to theaforementioned method, wherein said first composition is injected intosaid lumen through a catheter or a syringe.

In certain embodiments, the present invention relates to theaforementioned method, wherein the catheter is a dual lumen catheter ora triple lumen catheter.

In certain embodiments, the present invention relates to theaforementioned method, wherein said lumen is or is a portion of akidney, gall bladder, ureter, urinary bladder, pancreas, salivary gland,small intestine or large intestine.

In certain embodiments, the present invention relates to theaforementioned method, wherein said lumen is or is a portion of a ureteror kidney.

In certain embodiments, the present invention relates to theaforementioned method, wherein said calculi is a kidney stone,pancreatic stone, salivary stone, or biliary stone.

In certain embodiments, the present invention relates to theaforementioned method, wherein said calculi is a kidney stone.

In certain embodiments, the present invention relates to theaforementioned method, wherein said mammal is a human.

In certain embodiments, the present invention relates to theaforementioned method, wherein said second composition comprises acontrast-enhancing agent.

In certain embodiments, the present invention relates to theaforementioned method, wherein said contrast-enhancing agent is selectedfrom the group consisting of radiopaque materials, paramagneticmaterials, heavy atoms, transition metals, lanthanides, actinides, dyes,and radionuclide-containing materials. \

Another aspect of the present invention relates to a method of treatinglithiasis, comprising the steps of:

injecting into a lumen of a mammal at a first distance upstream from acalculi a first composition comprising an inverse thermosensitivepolymer, wherein said first composition does not contact said calculi;thereby forming a polymer plug;

optionally injecting into said lumen at a second distance upstream fromsaid calculi a second composition, wherein said second composition doesnot contact said calculi; and

allowing peristalsis to cause said polymer plug to traverse said lumen,thereby forcing said calculi from said lumen.

In certain embodiments, the present invention relates to theaforementioned method, wherein said second composition is injected intosaid lumen.

In certain embodiments, the present invention relates to theaforementioned method, wherein said second composition is injected intosaid lumen.

In certain embodiments, the present invention relates to theaforementioned method, wherein said first position is between about 1 cmand about 5 cm upstream of said calculi.

In certain embodiments, the present invention relates to theaforementioned method, wherein said first position is between about 2 cmand about 4 cm upstream of said calculi.

In certain embodiments, the present invention relates to theaforementioned method, wherein said first position is about 3 cmupstream of said calculi.

In certain embodiments, the present invention relates to theaforementioned method, wherein the distance between said first positionand said second position is less than about 3 mm.

In certain embodiments, the present invention relates to theaforementioned method, wherein the distance between said first positionand said second position is less than about 1 mm.

In certain embodiments, the present invention relates to theaforementioned method, wherein the distance between said first positionand said second position is less than about 0.5 mm.

In certain embodiments, the present invention relates to theaforementioned method, wherein the distance between said first positionand said second position is less than about 0.1 mm.

In certain embodiments, the present invention relates to theaforementioned method, wherein said first composition is injected intosaid lumen through a percutaneous access device.

In certain embodiments, the present invention relates to theaforementioned method, wherein said first composition is injected intosaid lumen through a catheter or a syringe.

In certain embodiments, the present invention relates to theaforementioned method, wherein the catheter is a dual lumen catheter ora triple lumen catheter.

In certain embodiments, the present invention relates to theaforementioned method, wherein said lumen is or is a portion of akidney, gall bladder, ureter, urinary bladder, pancreas, salivary gland,small intestine or large intestine.

In certain embodiments, the present invention relates to theaforementioned method, wherein said lumen is or is a portion of a ureteror kidney.

In certain embodiments, the present invention relates to theaforementioned method, wherein said calculi is a kidney stone,pancreatic stone, salivary stone, or biliary stone.

In certain embodiments, the present invention relates to theaforementioned method, wherein said calculi is a kidney stone.

In certain embodiments, the present invention relates to theaforementioned method, wherein said mammal is a human.

In certain embodiments, the present invention relates to theaforementioned method, wherein said second composition comprises acontrast-enhancing agent.

In certain embodiments, the present invention relates to theaforementioned method, wherein said contrast-enhancing agent is selectedfrom the group consisting of radiopaque materials, paramagneticmaterials, heavy atoms, transition metals, lanthanides, actinides, dyes,and radionuclide-containing materials.

In certain embodiments, the present invention relates to theaforementioned method, wherein said inverse thermosensitive polymer is ablock copolymer, random copolymer, graft polymer, or branched copolymer.

In certain embodiments, the present invention relates to theaforementioned method, wherein said inverse thermosensitive polymer is ablock polymer or a branched copolymer.

In certain embodiments, the present invention relates to theaforementioned method, wherein said inverse thermosensitive polymer isan optionally purified poloxamer or poloxamine.

In certain embodiments, the present invention relates to theaforementioned method, wherein said inverse thermosensitive polymer isoptionally purified and selected from the group consisting of poloxamine1107, poloxamine 1307, poloxamer 338 and poloxamer 407.

In certain embodiments, the present invention relates to theaforementioned method, wherein said inverse thermosensitive polymer isan optionally purified poloxamer 407.

In certain embodiments, the present invention relates to theaforementioned method, wherein said first composition has a transitiontemperature of between about 10° C. and 40° C.

In certain embodiments, the present invention relates to theaforementioned method, wherein said first composition has a transitiontemperature of between about 15° C. and 30° C.

In certain embodiments, the present invention relates to theaforementioned method, wherein said first composition has a transitiontemperature of about 25° C.

In certain embodiments, the present invention relates to theaforementioned method, wherein said first composition comprises about 5%to about 30% of said inverse thermosensitive polymer.

In certain embodiments, the present invention relates to theaforementioned method, wherein said first composition comprises about10% to about 25% said inverse thermosensitive polymer.

In certain embodiments, the present invention relates to theaforementioned method, wherein the inverse thermosensitive polymer has apolydispersity index from about 1.5 to 1.0.

In certain embodiments, the present invention relates to theaforementioned method, wherein the inverse thermosensitive polymer has apolydispersity index from about 1.2 to 1.0.

In certain embodiments, the present invention relates to theaforementioned method, wherein the inverse thermosensitive polymer has apolydispersity index from about 1.1 to 1.0.

In certain embodiments, the present invention relates to theaforementioned method, wherein said inverse thermosensitive polymer isan optionally purified poloxamer or poloxamine; and said firstcomposition has a transition temperature of between about 10° C. and 40°C.

In certain embodiments, the present invention relates to theaforementioned method, wherein said inverse thermosensitive polymer isan optionally purified poloxamer or poloxamine; and said firstcomposition has a transition temperature of between about 15° C. and 30°C.

In certain embodiments, the present invention relates to theaforementioned method, wherein said inverse thermosensitive polymer isan optionally purified poloxamer or poloxamine; and said firstcomposition has a transition temperature of about 25° C.

Another aspect of the present invention relates to a method of treatinglithiasis, comprising the steps of:

injecting into a lumen of a mammal at a first distance upstream from acalculi a first composition, wherein said first composition does notcontact said calculi;

injecting into said lumen at a second distance upstream from saidcalculi a second composition, wherein said second composition does notcontact said calculi; wherein said first composition and said secondcomposition admix, thereby forming a polymer plug;

optionally injecting into said lumen at a third distance upstream fromsaid calculi a third composition, wherein said third composition doesnot contact said calculi; and

allowing peristalsis to cause said polymer plug to traverse said lumen,thereby forcing said calculi from said lumen.

In certain embodiments, the present invention relates to theaforementioned method, wherein said third composition is injected intosaid lumen. In certain embodiments, the present invention relates to theaforementioned method, wherein said third composition is injected intosaid lumen.

In certain embodiments, the present invention relates to theaforementioned method, wherein said second composition is injected intosaid lumen.

In certain embodiments, the present invention relates to theaforementioned method, wherein said first position is between about 1 cmand about 5 cm upstream of said calculi.

In certain embodiments, the present invention relates to theaforementioned method, wherein said first position is between about 2 cmand about 4 cm upstream of said calculi.

In certain embodiments, the present invention relates to theaforementioned method, wherein said first position is about 3 cmupstream of said calculi.

In certain embodiments, the present invention relates to theaforementioned method, wherein the distance between said first positionand said second position is less than about 3 mm.

In certain embodiments, the present invention relates to theaforementioned method, wherein the distance between said first positionand said second position is less than about 1 mm.

In certain embodiments, the present invention relates to theaforementioned method, wherein the distance between said first positionand said second position is less than about 0.5 mm.

In certain embodiments, the present invention relates to theaforementioned method, wherein the distance between said first positionand said second position is less than about 0.1 mm.

In certain embodiments, the present invention relates to theaforementioned method, wherein said first and second compositions areinjected into said lumen through a percutaneous access device.

In certain embodiments, the present invention relates to theaforementioned method, wherein said first and second compositions areinjected into said lumen through a catheter or a syringe.

In certain embodiments, the present invention relates to theaforementioned method, wherein the catheter is a dual lumen catheter ora triple lumen catheter.

In certain embodiments, the present invention relates to theaforementioned method, wherein said lumen is or is a portion of akidney, gall bladder, ureter, urinary bladder, pancreas, salivary gland,small intestine or large intestine.

In certain embodiments, the present invention relates to theaforementioned method, wherein said lumen is or is a portion of a ureteror kidney.

In certain embodiments, the present invention relates to theaforementioned method, wherein said calculi is a kidney stone,pancreatic stone, salivary stone, or biliary stone.

In certain embodiments, the present invention relates to theaforementioned method, wherein said calculi is a kidney stone.

In certain embodiments, the present invention relates to theaforementioned method, wherein said mammal is a human.

In certain embodiments, the present invention relates to theaforementioned method, wherein said second composition comprises acontrast-enhancing agent.

In certain embodiments, the present invention relates to theaforementioned method, wherein said contrast-enhancing agent is selectedfrom the group consisting of radiopaque materials, paramagneticmaterials, heavy atoms, transition metals, lanthanides, actinides, dyes,and radionuclide-containing materials.

In certain embodiments, the present invention relates to theaforementioned method, wherein said first composition comprises ananionic, cationic, or non-ionically crosslinkable polymer.

In certain embodiments, the present invention relates to theaforementioned method, wherein said first composition comprises apolymer selected from the group consisting of alginic acid, sodiumalginate, potassium alginate, sodium gellan, potassium gellan, carboxymethyl cellulose, hyaluronic acid and polyvinyl alcohol.

In certain embodiments, the present invention relates to theaforementioned method, wherein said second composition comprisesphosphate, citrate, borate, succinate, maleate, adipate, oxalate,calcium, magnesium, barium, strontium, or a combination thereof.

In certain embodiments, the present invention relates to theaforementioned method, wherein said first composition comprises apolymer selected from the group consisting of alginic acid, sodiumalginate, potassium alginate, sodium gellan and potassium gellan; andsaid second composition comprises calcium, magnesium or barium.

In certain embodiments, the present invention relates to theaforementioned method, wherein said first composition comprises apolymer selected from the group consisting of alginic acid, sodiumalginate or potassium alginate; and said second composition comprisescalcium.

In certain embodiments, the present invention relates to theaforementioned method, wherein said first composition comprises apolymer selected from the group consisting of sodium gellan andpotassium gellan; and said second composition comprises magnesium.

In certain embodiments, the present invention relates to theaforementioned method, wherein said first composition compriseshyaluronic acid; and said second composition comprises calcium.

In certain embodiments, the present invention relates to theaforementioned method, wherein said first composition comprisespolyvinyl alcohol; and said second composition comprises borate.

In one embodiment the polymer solution can be introduced through acatheter. The catheter may be a dilatation catheter. In one embodiment,the catheter is 3-10 French in size, and more preferably 3-6 French. Inanother embodiment, a catheter can be used to dispense one or morefluids other than, or in addition to, the polymer solution. In saidembodiment the catheter may be a multiple lumen catheter with one lumenfor the delivery of the polymer solution, other lumen for the deliveryof other fluids such as a contrast agent solution.

In another embodiment, the syringe or other mechanism may be used toinject the polymer solution into the body can be, for example, a 1-100cc syringe, a 1-50 cc syringe or a 1-5 cc. Pressure applied to thesyringe can be applied by hand or by an automated syringe pusher.

EXEMPLIFICATION

The invention now being generally described, it will be more readilyunderstood by reference to the following examples, which are includedmerely for purposes of illustration of certain aspects and embodimentsof the present invention, and are not intended to limit the invention.

Example 1 Gelation Temperature of Selected Pluronic® and Tetronic®Polymer Solutions

The polymer was weighed into a plastic tube. To achieve the requiredconcentration the weight was multiplied by 4, for 25 weight percent (w%), and by 5, for 20 weight percent (w %), and the required final weightwas achieved by adding saline. The solutions were placed in the fridgeat 4° C. and usually were ready within 24 hours. Gelation points weremeasured in a Brookfield viscometer and the point at which viscosityexceeded the range of the plate/cone (greater than about 102,000 cP) wascalled the gelation temperature.

TABLE 1 polymer concentration temperature Tetronic 1107 25 w % 27° C.Tetronic 1107 20 w % 34° C. Purified Tetronic 1107 25 w % 22° C.Purified Tetronic 1107 20 w % 32.5° C.  Tetronic 1307 25 w % 24.5° C. Tetronic 1307 20 w % 31° C. Purified Tetronic 1307 25 w % 20° C.Purified Tetronic 1307 20 w % 26° C. Pluronic F108 25 w % 26° C.Pluronic F108 20 w % 60° C. Purified Pluronic F108 25 w % 19° C.Purified Pluronic F108 20 w % 26° C.

Example 2 Gelation Temperature of Selected Pluronic® and Tetronic®Polymer Solutions with Iodinated Contrast Agent

Purified polymers were weighed into 50 mL centrifuge tubes and a 1:1mixture of saline and 100% Omnipaque 300 were added until a specificweight percentage was reached. Gelation points were measured in aBrookfield viscometer and the point at which the viscosity exceeded therange of the plate/cone (greater than about 102,000 cP) was called thegelation point. All solutions were further heated to 37° C. to ascertainthat the material still exceeded the viscosity range and remained a gel.All gels passed.

TABLE 2 polymer concentration temperature Purified Tetronic 1107 20 w % 24° C. Purified Tetronic 1307 21 w % 26.5° C. Purified Pluronic F108 18w % 21.5° C. Purified Pluronic F127 18 w %  18° C.

Example 3 Dissolution Time Under Static Conditions in Saline

The dissolution of the purified poloxamer 407 gel was tested byinjecting 0.5 milliliter of the gel into a petri dish covered in salineat 37° C. The gel was visualized by small addition of methylene blue andthe dissolution of the gel was followed visually. Two different shapesof the gels were used for the dissolution tests: a sphere which has theleast amount of surface area; and a string, which has the highestsurface area, in which a 20 gauge syringe was used to extrude the stringof polymer onto the bottom of the Petri dish.

The petri dish was not disturbed and every minute, the petri dish wasobserved visually and complete dissolution was confirmed by swirling thepetri dish.

The dissolution was dependent on the concentration of the polymer. Thelower the polymer concentration, the faster the gel dissolved asdepicted in the FIG. 5. Further, the dissolution was dependent on thesurface area in direct contact with the surrounding liquid, thesphere-shaped gel taking longer to dissolve than the string.

These in-vitro experiments probably still overestimate the realdissolution times as there was no pulsatile force on the gel, whichwould probably speed up the dissolution.

Example 4 Dissolution Time Under Static Conditions in Urine

The dissolution of the 22.5% purified poloxamer 407 gel was tested byinjecting 2.5 milliliter of the gel into a petri dish covered in about100 mL urine at 37° C. A syringe without a needle was used to extrude astring of polymer onto the bottom of the Petri dish. The gel wasvisualized by small addition of methylene blue and the dissolution ofthe gel was followed visually. Upon extrusion the string broke in two.The petri dish was not disturbed and every minute, the petri dish wasobserved visually and complete dissolution was confirmed by swirling thepetri dish. The complete dissolution time (about 26 minutes) wasidentical for the two strings.

Example 5 Pig Ureter In-Vivo Experiments

A 22.5 w % solution of purified Poloxamer PF127, colored with methyleneblue, in a Medallion 5 ml syringe was used. In each of the three pigs,an artificial stone, made of plaster of Paris, was surgically implantedin the right ureter a few centimeters above the site of the incision.The solution was then injected behind the stone through the sameincision site, using a 3F catheter [Embocath HIC 100 from BioSphereMedical, lot#03W-6930]. Immediately prior to the injection the catheterwas flushed with 10 cc of cold saline to keep it cool during theinjection and avoid hardening of the polymer within the catheter. Eachprocedure was monitored with a camera inserted in the ureter between thestone and the incision site.

Pig #1—3 ml of solution were injected behind the stone that occluded ca.¼ to ⅓ of the cross-section of the ureter, and created a well visibleblue polymer plug that completed occluded the ureter behind the stone.After a little over 1 minute, the polymer plug or some urineaccumulating behind it created contraction waves of the ureteral walls(peristalsis) which forced the plug to slide forward towards the cameraand out of the ureter, carrying with it the entire stone, without anyneed for lithotripsy.

Pig #2—Same as the 1^(st) pig but the stone was slightly larger, andimmediately after the injection of the polymer lithotripsy (EHL) wasused to break the stone into small fragments. Within one minute of thecompletion of lithotripsy peristalsis started and the stone debris werepushed by the sliding plug out of the ureter.

Pig #3—Same as the 2^(nd) pig but the stone was even larger. Within oneminute of the completion of lithotripsy peristalsis started and thestone debris were pushed by the sliding plug out of the ureter.

INCORPORATION BY REFERENCE

All of the U.S. patents and U.S. patent application publications citedherein are hereby incorporated by reference.

EQUIVALENTS

Those skilled in the art will recognize, or be able to ascertain usingno more than routine experimentation, many equivalents to the specificembodiments of the invention described herein. Such equivalents areintended to be encompassed by the following claims.

What is claimed is:
 1. A method of treating lithiasis, comprising thesteps of: injecting into a lumen of a mammal at a first distanceupstream from a calculi a first composition comprising between 12 and 25weight percent of an inverse thermosensitive polymer, wherein said firstcomposition does not initially contact said calculi; thereby forming apolymer plug; and removing the calculi from the lumen by movement of thepolymer plug by peristalsis to traverse said lumen, thereby forcing saidcalculi from said lumen.
 2. The method of claim 1, further comprisinginjecting into said lumen a second composition at a second distanceupstream from said calculi wherein said second composition does notcontact said calculi.
 3. The method of claim 1, wherein said firstdistance is between about 1 cm and about 5 cm upstream of said calculi.4. The method of claim 2, wherein the distance between said firstdistance and said second distance is less than about 3 mm.
 5. The methodof claim 1, wherein said first composition is injected into said lumenthrough a percutaneous access device.
 6. The method of claim 1, whereinsaid lumen is or is a portion of a kidney, gall bladder, ureter, urinarybladder, pancreas, salivary gland, small intestine, or large intestine.7. The method of claim 1, wherein said lumen is or is a portion of aureter or kidney.
 8. The method of claim 1, wherein said calculi is akidney stone, pancreatic stone, salivary stone, or biliary stone.
 9. Themethod of claim 1, wherein said calculi is a kidney stone.
 10. Themethod of claim 2, wherein said second composition comprises acontrast-enhancing agent.
 11. The method of claim 10, wherein saidcontrast-enhancing agent is selected from the group consisting ofradiopaque materials, paramagnetic materials, heavy atoms, transitionmetals, lanthanides, actinides, dyes, and radionuclide-containingmaterials.
 12. The method of claim 1, wherein said inversethermosensitive polymer is an optionally purified poloxamer orpoloxamine.
 13. The method of claim 1, wherein said inversethermosensitive polymer is optionally purified and selected from thegroup consisting of poloxamine 1107, poloxamine 1307, poloxamer 338 andpoloxamer
 407. 14. The method of claim 1, wherein said inversethermosensitive polymer is an optionally purified poloxamer 407.